JP2012009677A - Piezoelectric film and piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric film having high piezoelectric performance, and to provide a piezoelectric element.SOLUTION: The piezoelectric film is a composite oxide having a perovskite structure oriented preferentially on the (100) plane and represented by a composition formula: Pb[(ZrTi)Nb]O. In the formula, x is in the range of 0<x<1, y is in the range of 0.13≤y≤0.25, and the ratio of diffraction peak intensity I(100) from a perovskite (100) plane and diffraction peak intensity I(200) from a perovskite (200) plane, measured by X-ray diffraction method, satisfies a relation: I(100)/I(200)≥1.25.

Description

  The present invention relates to a piezoelectric film and a piezoelectric element, and more particularly to a piezoelectric film and a piezoelectric element having high piezoelectric performance.

  2. Description of the Related Art Conventionally, a piezoelectric element that combines a piezoelectric film having a piezoelectric effect that is displaced by applying a voltage and an electrode that applies a voltage to the piezoelectric film is known as an actuator. The piezoelectric film is a thin film and is very useful because it is advantageous for miniaturization. However, since the piezoelectric performance does not change, there is a problem that sufficient device performance cannot be exhibited.

  As the piezoelectric material, PZT (lead zirconate titanate) and a PZT substitution system in which part of the A site and / or B site of PZT is substituted with other elements are known. It is known that PZT to which a donor ion having a valence higher than that of a substituted ion is added has improved piezoelectric performance as compared with intrinsic PZT.

For example, Patent Document 1 below describes a piezoelectric film in which atoms at the B site are substituted with Ta or Nb in a range of 5% to 20%, and SiO ₂ or GeO ₂ is contained as an additive. .

JP 2009-221037 A

  In recent years, there has been an increasing demand for piezoelectric films having high piezoelectric performance. The present invention provides a piezoelectric film and a piezoelectric element having higher piezoelectric performance.

In order to achieve the above object, claim 1 of the present invention has a perovskite structure preferentially oriented in the (100) plane, and has the composition formula: Pb _{1 + δ} [(Zr _x Ti _1-x ) _1-y Nb _y ] O a composite oxide represented by _z , wherein x is in a range of 0 <x <1, y is in a range of 0.13 ≦ y ≦ 0.25, and is measured by an X-ray diffraction method The ratio of the diffraction peak intensity I (100) from the perovskite (100) plane to the diffraction peak intensity I (200) from the perovskite (200) plane satisfies I (100) / I (200) ≧ 1.25 A piezoelectric film is provided.
(Δ = 0 and z = 3 are standard, but these values may deviate from the reference value within a range where a perovskite structure can be taken.)
According to the first aspect, since the amount of Nb is set to 13% or more, piezoelectric characteristics and dielectric characteristics can be improved. Further, by satisfying I (100) / I (200) ≧ 1.25, it can be confirmed that Pb is arranged at an effective position in the perovskite lattice, and sufficient piezoelectric performance can be obtained. Further, by defining the ratio of I (100) / I (200) ≧ 1.25, the amount of unstable Pb ions in the crystal can be reduced, so that continuous driving durability can be improved. .

  A second aspect of the present invention is characterized in that, in the first aspect, a ratio of the diffraction peak intensity I (100) to the diffraction peak intensity I (200) satisfies I (100) / I (200) ≧ 1.29. .

  A third aspect is characterized in that, in the second aspect, y is in a range of 0.19 ≦ y ≦ 0.25.

  According to claim 2 and claim 3, when the doping amount of Nb is set to 19% or more and I (100) / I (200) is set to 1.29 or more, higher piezoelectric characteristics / dielectric A piezoelectric film having characteristics can be provided.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the crystal phase includes a rhombohedral phase.

  Although the spontaneous polarization of the rhombohedral phase is in the (111) direction, it is known to exhibit a large piezoelectric constant when an electric field in the (100) direction is applied.

  According to the fourth aspect, since the crystal layer includes the rhombohedral phase, it is possible to provide a piezoelectric film having higher piezoelectric performance due to the effects described above.

  A fifth aspect is characterized in that in any one of the first to fourth aspects, the film thickness is 2 μm or more.

  According to the present invention, by defining the ratio of I (100) / I (200), continuous driving durability can be improved, and by increasing the film thickness, durability can be further increased. Can be improved.

A sixth aspect is characterized in that the piezoelectric constant d ₃₁ is 220 pm / V or more in any one of the first to fifth aspects.

A seventh aspect is characterized in that, in the sixth aspect, the piezoelectric constant d ₃₁ is 250 pm / V or more.

According to the sixth or seventh aspect, since the piezoelectric constant d ₃₁ of the piezoelectric film is set to 220 pm / V or more, more preferably 250 pm / V or more, sufficient piezoelectric performance can be obtained.

  An eighth aspect is characterized in that, in any one of the first to seventh aspects, the crystal structure is a columnar crystal structure extending in a thickness direction.

  According to the eighth aspect, since the crystal structure is a columnar crystal structure extending in the thickness direction, a thick piezoelectric film can be formed.

  A ninth aspect is characterized in that in any one of the first to eighth aspects, the film is formed by a sputtering method.

  According to the ninth aspect, since the piezoelectric film is formed by the sputtering method, it is possible to prevent the occurrence of lateral streaks due to the stacked crystallization and improve the durability.

  According to a tenth aspect of the present invention, there is provided a piezoelectric element comprising the piezoelectric film according to any one of the first to ninth aspects and an electrode for applying an electric field, in order to achieve the object. To do.

  According to the tenth aspect, a piezoelectric element having high piezoelectric performance can be provided by using the piezoelectric film of the present invention.

  According to the piezoelectric film of the present invention, 13% or more of Nb is contained, and the diffraction peak intensity ratio from the (100) plane and the (200) plane is set to a predetermined value or more, so that sufficient piezoelectric performance can be obtained. it can. Further, by using the piezoelectric film of the present invention for a piezoelectric element, a piezoelectric element having sufficient performance can be provided.

It is sectional drawing which shows the structure of a piezoelectric element provided with the piezoelectric material film which concerns on this invention, and an inkjet recording head. It is a figure which shows an example of the manufacturing apparatus which manufactures the piezoelectric film of this invention. 1 is an overall configuration diagram showing an outline of an inkjet recording apparatus. 6 is a view showing a manufacturing apparatus for manufacturing a piezoelectric film of Comparative Example 2. FIG. 2 is an XRD diffraction pattern of a piezoelectric film manufactured in Example 1. FIG. It is a table | surface figure which shows the result of an Example. 4 is an XRD diffraction pattern of a piezoelectric film manufactured in Example 3. FIG. 3 is an XRD diffraction pattern of a piezoelectric film manufactured in Comparative Example 2. FIG. It is a graph which shows the relationship between Nb addition amount and dielectric constant (epsilon) of an Example. Is a graph showing the relationship between the added amount of Nb and the piezoelectric constant d ₃₁ of Example.

  Hereinafter, preferred embodiments of a piezoelectric film and a piezoelectric element according to the present invention will be described with reference to the accompanying drawings.

[Piezoelectric element, inkjet recording head]
With reference to FIG. 1, the structure of a piezoelectric element and an ink jet recording head provided with a piezoelectric film according to the present invention will be described. FIG. 1 is a cross-sectional view of a main part of an ink jet recording head. In order to facilitate visual recognition, the scale of the constituent elements is appropriately changed from the actual one.

  The ink jet recording head 3 according to the present embodiment is roughly arranged on the back surface side of the piezoelectric actuator 2 with an ink chamber (liquid storage chamber) 21 for storing ink and an ink discharge port (for discharging ink from the ink chamber 21 to the outside). An ink nozzle (liquid storage and discharge member) 20 having a liquid discharge port 22 is attached.

  In the ink jet recording head, the electric field strength applied to the piezoelectric element 1 is increased or decreased to expand or contract the piezoelectric element 1, thereby controlling the amount of ink discharged from the ink chamber 21.

  In the piezoelectric actuator 2, a vibration plate 16 that vibrates due to expansion and contraction of the piezoelectric film 13 is attached to the back surface of the substrate 11 of the piezoelectric element 1.

  Instead of attaching the diaphragm 16 and the ink nozzle 20 which are members independent of the substrate 11, a part of the substrate 11 may be processed into the diaphragm 16 and the ink nozzle 20. For example, the ink chamber 21 can be formed by etching the substrate 11 from the back side, and the diaphragm 16 and the ink nozzle 20 can be formed by processing the substrate itself.

  The piezoelectric element 1 is an element in which a lower electrode layer 12, a piezoelectric film 13, and an upper electrode layer 14 are sequentially laminated on the surface of a substrate 11. The piezoelectric film 13 includes a lower electrode layer 12 and an upper electrode layer 14. Thus, an electric field is applied in the film thickness direction.

  The piezoelectric actuator 2 is a flexural vibration mode actuator, and the lower electrode layer 12 is patterned together with the piezoelectric film 13 so that the drive voltage can be varied for each ink chamber 21. The piezoelectric element 1 is also provided with a drive driver 15 that performs drive control to vary the voltage applied to the lower electrode layer 12.

In the piezoelectric element 1 of the present embodiment, the substrate 11 is not particularly limited, and examples thereof include silicon, glass, stainless steel (SUS), yttrium stabilized zirconia (YSZ), SrTiO ₃ , alumina, sapphire, and silicon carbide. . As the substrate 11, a laminated substrate such as an SOI substrate in which a SiO ₂ film and a Si active layer are sequentially laminated on a silicon substrate may be used. Further, a buffer layer for improving the lattice matching, an adhesion layer for improving the adhesion between the electrode and the substrate, or the like may be provided between the substrate 11 and the lower electrode layer 12.

The main component of the lower electrode layer 12 is not particularly limited, and examples thereof include metals or metal oxides such as Au, Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ , and SrRuO ₃ , and combinations thereof.

  The main component of the upper electrode layer 14 is not particularly limited, and examples thereof include materials exemplified for the lower electrode layer 12, electrode materials generally used in semiconductor processes such as Al, Ta, Cr, and Cu, and combinations thereof. Can be mentioned.

  The thicknesses of the lower electrode layer 12 and the upper electrode layer 14 are not particularly limited and are preferably 50 to 500 nm.

  The piezoelectric film 13 has a perovskite structure preferentially oriented in the (100) plane. Note that the preferential orientation refers to a state in which the orientation direction of the crystal is not disordered and a specific crystal plane is oriented in a substantially constant direction. Specifically, “preferentially oriented in the (100) plane” means diffraction of the (100) plane, the (110) plane, and the (111) plane that occurs when the piezoelectric film is measured by the X-ray diffraction wide angle method. It means that the intensity ratio (100) / ((100) + (110) + (111)) is larger than 0.5.

  The piezoelectric film 13 is made of one or more perovskite oxides (P) represented by the following formula.

Composition formula (P): Pb _{1 + δ} [(Zr _x Ti _1-x ) _1-y Nb _y ] O _z
x is in the range of 0 <x <1, and y is in the range of 0.13 ≦ y ≦ 0.25. (Δ = 0 and z = 3 are standard, but these values may deviate from the reference value within a range where a perovskite structure can be taken.)
Further, the ratio of the diffraction peak intensity I (100) from the perovskite (100) plane and the diffraction peak intensity I (200) from the perovskite (200) plane measured by the X-ray diffraction method of the piezoelectric film 13 is I ( 100) / I (200) ≧ 1.25.

  Preferably, y is in the range of 0.19 ≦ y0.25, and I (100) / I (200) ≧ 1.29.

  The value of I (100) / I (200) correlates with the amount of unstable Pb ions present in the crystal. It is shown that the smaller this value is, the more Pb ions inhibit the piezoelectric function in the crystal. Moreover, if there are many unstable Pb ions in the crystal, the continuous durability is also adversely affected.

[Method for forming piezoelectric film]
The method for forming the piezoelectric film 13 is not particularly limited, and vapor phase growth methods such as sputtering, plasma CVD, MOCVD, and PL; liquid phase methods such as sol-gel and organometallic decomposition; and Examples include aerosol deposition. Vapor phase epitaxy is preferred because the film formation conditions can be easily changed during film formation. Further, by performing the vapor phase growth method, it is possible to suppress the generation of lateral streaks during film formation, and it is possible to form a highly durable piezoelectric film.

  In the present invention, in order to reduce the amount of unstable Pb ions in the crystal (increase the value of I (100) / I (200)), the piezoelectric film is formed so that the ion energy colliding with the substrate is increased. The film is formed.

  The production of the piezoelectric film by the vapor phase growth method can be applied to a film forming apparatus that forms a film containing a constituent element of a target on a substrate using plasma with a base material and a target facing each other. Applicable film formation methods include bipolar sputtering, tripolar sputtering, direct current sputtering, high frequency sputtering (RF sputtering), ECR sputtering, magnetron sputtering, counter target sputtering, pulse sputtering, and A sputtering method such as an ion beam sputtering method can be given. Examples of the vapor deposition method to which the present invention can be applied include an ion plating method and a plasma CVD method in addition to the sputtering method. In the present embodiment, a high frequency sputtering method (RF sputtering method) will be described as an example.

  FIG. 2 shows an example of a manufacturing apparatus for manufacturing the piezoelectric film of the present invention. A film forming apparatus (high-frequency sputtering apparatus) 200 shown in FIG. 2 is capable of mounting a substrate B, a substrate holder 211 that can heat the mounted substrate B to a predetermined temperature, and a target on which a target T can be mounted. A vacuum vessel 210 provided with a holder 212 is schematically configured. In the apparatus shown in FIG. 2, the vacuum vessel 210 is a film forming chamber.

  In the vacuum vessel 210, the substrate holder 211 and the target holder 212 are spaced apart so as to face each other. The target holder 212 is connected to a high-frequency power source (RF power source) 213 disposed outside the vacuum vessel 210, and the target holder 212 serves as a plasma power source (cathode electrode) for generating plasma. In FIG. 2, a high frequency power source 213 and a target holder 212 that functions as a plasma electrode (cathode electrode) are provided as plasma generating means 214 for generating plasma in the vacuum vessel 210.

  The substrate B is not particularly limited, and can be appropriately selected depending on applications such as a Si substrate, an oxide substrate, a glass substrate, and various flexible substrates. The composition of the target T is selected according to the composition of the film to be formed.

The film forming apparatus 200 includes a gas introduction unit 217 that introduces a gas G to be converted into plasma into the vacuum vessel 210 and a gas discharge pipe 218 that exhausts the gas V in the vacuum vessel 210. As the gas G, Ar, Ar / O ₂ mixed gas, or the like is used.

In FIG. 2, the wall surface in the vacuum vessel 210 is the floating wall 220 and is set to a floating potential. By setting the wall surface to a floating potential, it becomes the same potential as the plasma potential, so that it is difficult for the plasma component to reach the wall surface of the vacuum vessel 210 and the collision energy of ions against the substrate B can be increased. Therefore, Pb ions can be arranged at the A site of the perovskite structure (ABO ₃ ), and the amount of unstable Pb ions in the crystal can be reduced, so that the formed piezoelectric film obtains high piezoelectric performance. be able to. Further, since there are few unstable Pb ions, the ratio of diffraction peak intensities (I (100) / I (200)) measured by the X-ray diffraction method can be increased.

  In FIG. 2, the collision energy of ions to the substrate B is increased by setting the wall surface of the vacuum vessel 210 to a floating potential, but as another method, the anode area in the vacuum vessel 210 is reduced, or Control can also be performed by changing the impedance of the substrate B covered with an insulator.

  In the present invention, the B-site element of the perovskite structure of lead zirconate titanate (PZT) is replaced with Nb to improve the piezoelectric performance. A heterogeneous phase with no piezoelectric performance is likely to occur. Further, since Nb is pentavalent in the perovskite crystal, there is a tendency for unstable Pb atoms to increase due to the fact that charge neutrality does not hold as the Nb doping amount increases. Therefore, when doping Nb with 13% or more, it is necessary to give high energy to the incoming Pb ions during film formation. As described above, since the ion energy can be increased by using the piezoelectric film manufacturing apparatus shown in FIG. 2, a piezoelectric film having high piezoelectric performance can be manufactured.

  In the piezoelectric film thus formed, the crystal phase preferably includes a rhombohedral crystal phase. The crystal structure is preferably a columnar crystal structure extending in the thickness direction. With a columnar crystal structure, a thick piezoelectric film can be formed. The film thickness of the piezoelectric film is preferably 2 μm or more and 20 μm or less. By increasing the thickness of the piezoelectric film, a highly durable piezoelectric film can be formed. The average particle size of the many columnar crystals forming the piezoelectric film is not particularly limited, but is preferably 30 nm or more and 1 μm or less. If the average grain size of the columnar crystals is small, the influence of the domain boundary portion on the dielectric characteristics becomes large, and there is a possibility that desired piezoelectric performance cannot be obtained. Further, if the average grain size of the columnar crystals is large, the shape accuracy after patterning may be lowered.

The piezoelectric constant d ₃₁ of the piezoelectric film is preferably 220 pm / V or more, more preferably 250 pm / V or more. By setting the piezoelectric constant d ₃₁ in the above range, the piezoelectric film can be suitably used for a piezoelectric element and an ink jet recording head (liquid ejecting apparatus).

[Inkjet recording apparatus]
A configuration example of an ink jet recording apparatus including the ink jet recording head 3 (172M, 172K, 172C, 172Y) will be described with reference to FIG. FIG. 3 is an overall view of the apparatus.

  The inkjet recording apparatus 100 includes a plurality of colors from inkjet heads 172M, 172K, 172C, and 172Y on a recording medium 124 (sometimes referred to as “paper” for convenience) held on the impression cylinder (drawing drum 170) of the drawing unit 116. This is an impression cylinder direct drawing type ink jet recording apparatus that forms a desired color image by ejecting ink, and a treatment liquid (here, a coagulation treatment liquid) is applied onto the recording medium 124 before ink ejection. This is an on-demand type image forming apparatus to which a two-liquid reaction (aggregation) method for forming an image on a recording medium 124 by reacting a liquid and an ink liquid is applied.

  As shown in the figure, the ink jet recording apparatus 100 mainly includes a paper feeding unit 112, a treatment liquid application unit 114, a drawing unit 116, a drying unit 118, a fixing unit 120, and a discharge unit 122.

(Paper Feeder)
The paper feeding unit 112 is a mechanism that supplies the recording medium 124 to the processing liquid application unit 114, and the recording medium 124 that is a sheet is stacked on the paper feeding unit 112. The paper feed unit 112 is provided with a paper feed tray 150, and the recording medium 124 is fed from the paper feed tray 150 to the processing liquid application unit 114 one by one.

(Processing liquid application part)
The processing liquid application unit 114 is a mechanism that applies the processing liquid to the recording surface of the recording medium 124. The treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment in this example) in the ink applied by the drawing unit 116, and the ink comes into contact with the treatment liquid and the ink. And the solvent are promoted.

  The recording medium 124 to which the processing liquid is applied by the processing liquid applying unit 114 is transferred from the processing liquid drum 154 to the drawing drum 170 of the drawing unit 116 via the intermediate transport unit 126.

(Drawing part)
The drawing unit 116 includes a drawing drum (second transport body) 170, a sheet pressing roller 174, and ink jet recording heads 172M, 172K, 172C, and 172Y.

  The ink jet recording heads 172M, 172K, 172C, and 172Y are preferably full-line ink jet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area in the recording medium 124. On the ink ejection surface, a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area is formed. Each of the ink jet recording heads 172M, 172K, 172C, and 172Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 124 (the rotation direction of the drawing drum 170).

  A treatment liquid application unit is formed by ejecting droplets of the corresponding color ink from each of the ink jet recording heads 172M, 172K, 172C, and 172Y toward the recording surface of the recording medium 124 held in close contact with the drawing drum 170. In 114, the ink comes into contact with the processing liquid previously applied to the recording surface, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. Thereby, the color material flow on the recording medium 124 is prevented, and an image is formed on the recording surface of the recording medium 124.

  The recording medium 124 on which an image is formed by the drawing unit 116 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 118 via the intermediate conveyance unit 128.

(Drying part)
The drying unit 118 is a mechanism for drying moisture contained in the solvent separated by the color material aggregating action, and includes a drying drum (conveying body) 176 and a solvent drying device 178 as shown in FIG.

  The solvent drying device 178 is disposed at a position facing the outer peripheral surface of the drying drum 176 and includes an IR heater 182 and a hot air jet nozzle 180 disposed between the IR heaters 182.

  The recording medium 124 that has been dried by the drying unit 118 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 120 via the intermediate conveyance unit 130.

(Fixing part)
The fixing unit 120 includes a fixing drum 184, a halogen heater 186, a fixing roller 188, and an inline sensor 190. With the rotation of the fixing drum 184, the recording medium 124 is conveyed with the recording surface facing outward. The recording surface is preheated by the halogen heater 186, fixing processing by the fixing roller 188, and by the inline sensor 190. Inspection is performed.

  The fixing roller 188 is a roller member that heats and pressurizes the dried ink to weld the self-dispersing thermoplastic resin fine particles in the ink to form a film of the ink, and heats and pressurizes the recording medium 124. Composed.

  According to the fixing unit 120 configured as described above, the thermoplastic resin fine particles in the thin image layer formed by the drying unit 118 are heated and pressurized by the fixing roller 188 and are melted. Can be fixed and fixed.

  In addition, when a UV curable monomer is contained in the ink, after the water is sufficiently volatilized in the drying unit, the image is irradiated with UV at the fixing unit equipped with a UV irradiation lamp, so that the UV curable property is obtained. The monomer can be cured and polymerized to improve the image strength.

(Discharge part)
Subsequent to the fixing unit 120, a discharge unit 122 is provided. The discharge unit 122 includes a discharge tray 192, and a transfer drum 194, a conveyance belt 196, and a stretching roller 198 are provided between the discharge tray 192 and the fixing drum 184 of the fixing unit 120 so as to be in contact therewith. It has been. The recording medium 124 is sent to the conveyor belt 196 by the transfer drum 194 and discharged to the discharge tray 192.

  Although the drum conveyance type inkjet recording apparatus has been described with reference to FIG. 3, the present invention is not limited to this, and the invention can also be used in a belt conveyance type inkjet recording apparatus.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited thereto.

[Example 1]
Using a commercially available sputtering apparatus equipped with a 300φ target, as shown in FIG. An LCR circuit with variable impedance is connected to the substrate, and Vsub (substrate potential during film formation) during film formation can be changed by changing the impedance of the substrate.

Using Pb _1,3 (Zr _0.42 Ti _0.39 Nb _0.19 ) 0 ₃ as a target, 3 kW Rf sputtering was performed to prepare a PZT thin film (piezoelectric film). The film forming temperature was 500 ° C. The substrate used was an Ir lower electrode deposited by sputtering on a diaphragm structure fabricated by processing an SOI substrate by silicon RIE etching.

The XRD diffraction pattern of the obtained thin film is shown in FIG. It has a (100) single orientation, and its value is 1.29 when the intensity ratio of the I (100) / I (200) peak is taken. Further, when the dielectric constant ε was obtained from Cp and the piezoelectric constant d ₃₁ was obtained from the displacement of the diaphragm, ε = 1280 and d ₃₁ = 310. The results are shown in FIG.

[Example 2]
A PZT thin film was produced under the same conditions as in Example 1 except that PZT doped with Nb 20% at the B site was used as a target. In addition, Zr: Ti was adjusted and added so that it might become 52:48. In the following examples and comparative examples, the composition ratio of zirconium and titanium was fixed at Zr: Ti = 52: 48 regardless of the doping amount of Nb.

[Example 3]
A PZT thin film was produced under the same conditions as in Example 1 except that PZT doped with Nb 12.5% at the B site was used as a target. The XRD diffraction pattern of the thin film obtained in Example 3 is shown in FIG.

[Example 4]
A PZT thin film was produced under the same conditions as in Example 1 except that PZT doped with Nb 12.5% at the B site was used as a target.

[Comparative Example 1]
A PZT thin film was prepared under the same conditions as in Example 1 except that PZT doped with Nb 10% at the B site was used as a target.

[Comparative Example 2]
Using a commercially available sputtering apparatus equipped with a 300φ target, as shown in FIG. 4, the film forming chamber side wall surface was set to the ground potential, and the chamber wall around the substrate was set to the floating potential. Film formation was performed by Rf sputtering under the same film formation conditions as in Example 1 except that PZT doped with Nb 20% at the B site was used as a target.

The XRD diffraction pattern of the obtained thin film is shown in FIG. The intensity ratio of the (100) / (200) peak of the obtained film was 1.071. Further, when the dielectric constant ε and the piezoelectric constant d ₃₁ were determined, ε = 1280 and d ₃₁ = 310.

  As in the film forming apparatus shown in FIG. 4, when the film forming chamber side wall surface is a ground potential, the chamber wall around the substrate is a floating wall 220 ′, and the floating potential is set, a strong DC is applied toward the film forming chamber side surface in FIG. The electric field of the component is generated, and the electric field toward the bottom surface of the film forming chamber, that is, the substrate B is weakened. Therefore, it is considered that the ion collision energy is lowered and the piezoelectric performance is lowered.

[Comparative Example 3]
A PZT thin film was produced under the same apparatus and film formation conditions as in Comparative Example 2 except that PZT doped with Nb 17% at the B site was used as a target.

[Comparative Example 4]
A PZT thin film was produced under the same apparatus and film forming conditions as in Example 1 except that PZT doped with Nb 9% at the B site was used as a target.

[Comparative Example 5]
A PZT thin film was produced under the same apparatus and film formation conditions as in Example 1 except that PZT doped with Nb 6.5% at the B site was used as a target.

[Comparative Example 6]
A PZT thin film was produced under the same apparatus and film formation conditions as in Example 1 except that Pb _1.3 (Zr _0.52 Ti _0.48 ) O ₃ was used as a target.

[Comparative Example 7]
A PZT thin film was produced under the same apparatus and film forming conditions as in Comparative Example 2 except that PZT doped with Nb 13% at the B site was used as a target.

[result]
The results are shown in FIG. FIG. 9 shows the relationship between the Nb addition amount and the dielectric constant ε, and FIG. 10 shows the relationship between the Nb addition amount and the piezoelectric constant d ₃₁ . Driving durability is the number of times that dielectric breakdown or displacement deterioration occurred when driven continuously by applying a sine wave of 100 kHz, 25 Vp-p, offset voltage -12.5 V in an atmosphere of a temperature of 40 ° C. and a relative humidity of 80%. Based on the following criteria. The driving durability of Comparative Examples 4 to 6 was not tested because the numerical values of dielectric constant ε and piezoelectric constant d ₃₁ were low. Further, Vsub of Comparative Examples 5 and 6 was not measured.

◎ ・ ・ ・ Durability of driving ≧ 1 × 10 ¹¹ cycles ○ ・ ・ ・ 1 × 10 ¹¹ cycles> Durability of driving ≧ 1 × 10 ⁹ cycles × ・ ・ ・ 1 × 10 ⁹ cycles> Durability of driving FIGS. 10 shows that the piezoelectric characteristics and the dielectric characteristics tend to be improved by Nb doping to the B site. However, when I (100) / I (200) <1.25, it was confirmed that the characteristics were rapidly attenuated and sufficient characteristics could not be obtained. From these results, in order to obtain sufficient piezoelectric performance when applied to an inkjet head or the like, Nb ≧ 13%, I (100) / I (200) ≧ 1.25 shown by a thick frame in FIG. It can be confirmed that it needs to be satisfied.

  As shown in FIG. 2, the collision energy of ions against the substrate can be increased by setting the chamber wall surface of the sputtering apparatus to the floating potential and the substrate periphery to the ground potential, and unstable Pb ions in the crystal. Therefore, it is considered that high characteristics can be obtained. On the other hand, as shown in FIG. 4, by setting the chamber wall surface to the ground and the substrate periphery to the floating potential, the plasma becomes soft and cannot receive energy that Pb can sufficiently migrate on the substrate. As a result, Pb ions that are unstable and do not contribute to piezoelectricity are generated in the crystal, and the characteristics are considered to deteriorate. From the results of the examples, by setting the substrate potential Vsub to +10 V or less, the potential difference from the plasma potential can be increased, so that the ion energy can be increased.

  DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element, 2 ... Piezoelectric actuator, 3,172 ... Inkjet recording head, 11 ... Substrate, 12 ... Lower electrode layer, 13 ... Piezoelectric film, 14 ... Upper electrode layer, 15 ... Drive driver, 16 ... Vibration plate , 20 ... Ink nozzle (liquid storage and discharge member), 21 ... Ink chamber (liquid storage chamber), 22 ... Ink discharge port (liquid discharge port), 100 ... Inkjet recording apparatus, 112 ... Paper feed unit, 114 ... Processing Liquid applying unit 116 ... Drawing unit 118 ... Drying unit 120 ... Fixing unit 122 ... Discharging unit 124 ... Recording medium 200 ... Film forming device (high frequency sputtering device) 210 ... Vacuum container 211 ... Substrate Holder 212, target holder, 213, high frequency power supply (RF power supply), 217, gas introduction means, 218, gas discharge pipe, 220, floating wall, B, substrate, G, Scan, T ... target, V ... exhaust

Claims (10)

Having a perovskite structure preferentially oriented in the (100) plane;
Composition formula: Pb _{1 + δ} [(Zr _x Ti _1-x ) _1-y Nb _y ] O _z
Wherein x is in the range of 0 <x <1, y is in the range of 0.13 ≦ y ≦ 0.25,
The ratio of the diffraction peak intensity I (100) from the perovskite (100) plane and the diffraction peak intensity I (200) from the perovskite (200) plane measured by X-ray diffraction method is I (100) / I ( 200) A piezoelectric film satisfying ≧ 1.25.
(Δ = 0 and z = 3 are standard, but these values may deviate from the reference value within a range where a perovskite structure can be taken.)   2. The piezoelectric film according to claim 1, wherein a ratio of the diffraction peak intensity I (100) to the diffraction peak intensity I (200) satisfies I (100) / I (200) ≧ 1.29. .   The piezoelectric film according to claim 2, wherein y is in a range of 0.19 ≦ y ≦ 0.25.   The piezoelectric film according to claim 1, wherein the crystal phase includes a rhombohedral phase.   5. The piezoelectric film according to claim 1, wherein the film thickness is 2 μm or more. 6. The piezoelectric film according to claim 1, wherein the piezoelectric constant d ₃₁ is 220 pm / V or more. The piezoelectric film according to claim 6, the piezoelectric constant _{d 31} is equal to or is 250 pm / V or more.   The piezoelectric film according to any one of claims 1 to 7, wherein the crystal structure is a columnar crystal structure extending in a thickness direction.   The piezoelectric film according to claim 1, wherein the piezoelectric film is formed by a sputtering method.   A piezoelectric element comprising: the piezoelectric film according to any one of claims 1 to 9; and an electrode to which an electric field is applied.

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